<!DOCTYPE html>
<html>
    <head>

    </head>
    <body>
        <form action="form.php" method="POST">
            <select name="city">
                <optgroup label="山东省">
                    <option value="1" title="青岛"></option>
                    <option value="2" selected="selected">烟台</option>
                    <option value="3">济南</option>
                </optgroup>
                <optgroup label="北京市">
                    <option>海淀区</option>
                    <option>朝阳区</option>
                </optgroup>
            </select>
        </form>
    </body>
</html>